1. Field of the Invention
This invention relates to a solid catalyst component, a catalyst system and a process for producing .alpha.-olefin polymers using the catalyst system. More particularly, the invention relates to a novel solid catalyst component and catalyst system having a very high catalyst activity. This catalyst system can be used for the production of .alpha.-olefin polymers having a very low catalyst residue content and excellent in mechanical properties and workability.
2. Description of the Prior Art
It is generally known that a so-called Ziegler-Natta catalyst consisting of a compound of a transition metal of the groups IV to VI of the periodic table and an organo metal compound of a metal of the groups I to III of the periodic table is used for the production of polymers of .alpha.-olefins such as propylene, butene-1 and the like.
Particularly, a titanium chloride catalyst is used widely in the industrial production of .alpha.-olefin polymers.
In the above production, however, amorphous polymers are formed as a by-product besides .alpha.-olefin polymers of high stereoregularity and accordingly of high industrial value.
These amorphous polymers have a low industrial value and adversely affect the mechanical properties of .alpha.-olefin polymers when the .alpha.-olefin polymers are worked and used as a film, a fiber, etc.
Further, formation of amorphous polymers incurs the loss of raw material monomers and makes it requisite to instal a facility for removal of such amorphous polymers, causing very large industrial disadvantages.
Therefore, if no or substantially no amorphous polymer is formed, it can become a very large industrial advantage.
The .alpha.-olefin polymers obtained in the above polymerization contain a catalyst residue. This catalyst residue reduces the various properties of .alpha.-olefin polymers such as stability, workability and the like. Therefore, there is required a facility for removal of catalyst residue and for stabilization of .alpha.-olefin polymers.
The above problem (reduction in some properties of .alpha.-olefin polymers) can be improved by the increase of catalyst activity represented by the weight of .alpha.-olefin polymer produced per the unit weight of catalyst. This increase of catalyst activity also brings about no necessity of facility for catalyst residue removal as well as the lowering of production cost of .alpha.-olefin polymers.
There are various processes for production of titanium trichloride, such as (1) a process wherein titanium tetrachloride is reduced with hydrogen and then ground in a ball mill for activation, (2) a process wherein titanium tetrachloride is reduced with metallic aluminum and then ground in a ball mill for activation and (3) a process wherein titanium tetrachloride is reduced with an organo aluminum compound at a temperature of -30.degree. to 30.degree. C. and the resulting reduced solid product is heat-treated at a temperature of 120.degree. to 180.degree. C.
Titanium trichloride produced from any of the above processes is not fully satisfactory in any of catalyst activity and stereoregularity.
In polymerization of .alpha.-olefins using a catalyst system consisting of (1) a solid catalyst component obtained by, for example, (a) a process wherein titanium tetrachloride is reduced with an organo aluminum compound and the resulting reduced solid is treated with a complexing agent and reacted with titanium tetrachloride (U.S. Pat. No. 4,210,738) or (b) a process wherein a titanium compound represented by the general formula Ti(OR).sub.n X.sub.4-n is reduced with an organo aluminum compound and then treated with a mixture of an ether compound and titanium tetrachloride (U.S. Pat. No. 4,533,706) and (2) an organo aluminum compound, the stereoregularity of .alpha.-olefin polymers obtained is high but the catalyst activity is not satisfactory.
It is also known that titanium trichloride can be produced by reducing titanium tetrachloride with an organo magnesium compound such as a Grignard reagent.
Concerning the above, there is a process of reducing titanium tetrachloride with an organo magnesium compound and then treating the resulting solid product with a Lewis acid (British Pat. No. 1498862).
With the catalysts obtained from these processes, however, the catalyst activity is high but the stereoregularity of .alpha.-olefin polymers produced is not satisfactory.